Portable electronic devices such as Ultra Mobile PC (UMPC), laptop, personal digital assistants (PDAs), cellular phones, portable digital media players, and the like are becoming ubiquitous in modern technological societies. These devices offer specialized functionality in form factors small enough to carry in a pocket or some other small carrying bag. At least one reason why these types of devices are so popular is because display technology, which provides a convenient user interface, has advanced to a point where relatively small form factors are efficient and inexpensive. Indeed, even the most inexpensive portable electronic devices now include high frame rate color displays. However, conventional displays are not without some disadvantages.
For example, FIG. 1 is a prior art representation of a PDA 100. PDA 100 may include multipurpose navigation button 106 or any number of specific purpose navigation buttons 104A-D. These latter buttons may be utilized to provide convenient access to commonly utilized features. As illustrated, PDA 100 may further include a display 102 for displaying user selected information. Typically, display 102 is a liquid crystal display (LCD). LCDs have many desirable characteristics including high screen refresh rates (up to 85 Hz today for flat panels) which provide for a satisfying visual experience when rapidly switching between screens or when scrolling across a screen. However, typical displays having high screen refresh rates may suffer from poor readability because backlights, which are required in those displays, may be adversely affected by ambient lighting conditions. Eye strain is commonly reported by users and has been documented in some medical literature. Users of UMPCs or PDAs are familiar with the poor readability of LCDs under bright light or direct sunlight. In some examples, shading the screen or moving to a darker environment may be necessary to read an LCD.
Further, as may be appreciated, an LCD requires a backlight to illuminate the pixels being displayed. Because a backlight is required, PDAs may utilize power savings algorithms to power down the LCD after a specified time interval. In some conventional methods, various levels of backlight illumination may be utilized in a power saving algorithm. However, when a user is reading a document on a PDA, the time to complete reading may often exceed the power down time interval thus disrupting and diminishing a user's experience when the backlight is abruptly powered down. Furthermore, in some examples, where a user adjusts power settings to reduce power down events in order to avoid unwanted disruption, battery life may, in some examples, fall precipitously. One of the best battery-saving design is a bistable display, which has the ability to retain on-screen images even after the power has been turned off. In a bistable display, picture elements (i.e. pixels) are stable in two (or more) states. Thus, a bistable display requires power only when the content changes. Reading a bistable display is more like reading paper because no backlight element is required. Bistable displays may also be less stressful to eyes than typical high screen refresh rate displays such as an LCD.
It may, therefore, be desirable to provide a complementary display to conventional portable electronic device displays which provides a highly readable display that overcomes harsh ambient light conditions and that does not overly diminish battery life. As such, electronic devices having complementary bistable and refresh-based displays are provided herein.